The annual fuel utilization efficiency is a thermal efficiency measure of space-heating furnaces and boilers. Furnaces are rated by the AFUE ratio, which is the percent of heat produced for every dollar of fuel consumed. The higher the AFUE rating, the lower the fuel costs. Any furnace with an efficiency of 90 percent or higher is considered high-efficiency and carries the ENERGY STAR® label.
BTU: The British thermal unit is a traditional unit of heat, which is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.
COP: The coefficient of performance of a heat pump, refrigerator, or air conditioning system is a ratio of useful heating or cooling provided to work required. Higher COPs equate to lower operating costs.
EER: The energy-efficiency ratio is a metric used to measure how much cooling a system puts out for each unit of energy it consumes. EER is calculated by dividing an air conditioning unit’s British thermal unit (BTU) rating over its wattage. The higher the EER rating, the more efficiently the air conditioner operates. Any air conditioning unit with an efficiency of 12 EER or higher is considered a high-efficiency unit and carries the ENERGY STAR® label.
EF: The energy factor indicates a water heater’s overall energy efficiency based on the amount of hot water produced per unit of fuel consumed over a typical day. The higher the energy factor, the more efficient the water heater.
ENERGY STAR®: ENERGY STAR® is a government program that promotes energy-saving improvements by providing consumers with objective information about products. The ENERGY STAR® label indicates that a product uses less energy than other products in that category.
GPF: Gallons per flush is the measure of flow from a toilet. The lower the GPF of a toilet, the greater the savings of water.
GPM: Gallons per minute is the measure of flow from a showerhead or faucet. The lower the GPM of a faucet or showerhead, the greater the savings of water.
Level 2: Level 2 charging refers to the voltage that the electric vehicle charger uses (240 volts). Level 2 chargers come in a variety of amperages typically ranging from 16 amps to 40 amps. The two most common level 2 chargers are 16 and 30 amps, which also may be referred to as 3.3 kW and 7.2 kW respectively. These two amperages are the most common because they match the onboard charger on many current electric vehicles.
R-value: An insulating material’s resistance to conductive heat flow is measured or rated in terms of its thermal resistance or R-value—the higher the R-value, the greater the insulating effectiveness.
SEER: The seasonal energy-efficiency ratio is a metric used to measure how much cooling a system puts out for each unit of energy it consumes. The higher the SEER rating, the more efficiently the air conditioner operates. Any air conditioning unit with an efficiency of 15 SEER or higher is considered a high-efficiency unit and carries the ENERGY STAR® label.
SF: The solar factor measures the percentage of heat that passes through a solar panel’s glass. The higher the solar factor, the greater the solar gain for solar-thermal water heating units.
TE: Thermal efficiency is an efficiency measure for space-heating boilers, in lieu of the AFUE rating, that exceed 300,000 BTUs per hour. TE is also used to measure the efficiency of gas-fired water heaters that exceed 75,000 BTUs per hour.